High temperature resistant saline soluble fibres

ABSTRACT

A fibre is disclosed having a maximum use temperature of 1200° C. or more which comprises: SiO 2 &gt;64.25 wt % CaO&gt;18 wt % MgO&lt;17 wt % and in which the amount of MgO in mol % is greater than the amount of CaO in mol %. Such fibers have high solubility and low dustiness.

This application claims priority to Great Britain Application No.9921504.8 filed on Sep. 10, 1999 and Great Britain Application No.9924867.6 filed on Oct. 20, 1999 and International Application No.PCT/GB00/03275 filed on Aug. 24, 2000 and published in English asInternational Publication Number WO01/19744 A1 on Mar. 23, 2001, theentire contents of which are hereby incorporated by reference.

This invention relates to high temperature resistant saline solublefibres and particularly relates to calcium-magnesium-silicate fibres.

Calcium-magnesium-silicate fibres are known for example from WO89/12032,WO93/15028 and WO94/15883.

WO89/12032 first disclosed a broad class of fire-resistant salinesoluble fibres.

WO93/15028 showed that a class of the fibres of WO89/12032 were usableat temperatures up to 1000° C. or more.

WO94/15883 showed that some of the fibres of WO93/15028 had higher usetemperatures still, of up to 1260° C. or more, and indicated that suchfibres needed a SiO₂ excess (defined as the amount of SiO₂ remainingafter crystallisation of CaO, MgO and any ZrO₂ as silicates) of greaterthan 21.8 mol %.

WO97/16386 while falling in the general class ofcalcium-magnesium-silicate fibres looked to low calcium fibres to showuse temperatures of 1260° C. or more.

It is apparent that there are regions of the CaO—MgO—SiO₂ andCaO—MgO—SiO₂—ZrO₂ composition fields within which high temperatureperformance fibres can be made and other regions where they cannot

The applicants have now found a new and narrow range of compositionsthat are usable at temperatures of 1200° C. or more and even 1250° C. or1260° C. or more, and yet fall outside the scope of WO94/15883 andWO97/16386. These compositions preferably have little or no zirconia.

Accordingly the present invention provides a fibre having a maximum usetemperature of 1200° C. or more in which the amount of MgO in mol % isgreater than the amount of CaO in mol % and which comprises:—

-   -   SiO₂>64.25 wt %    -   CaO>18 wt %    -   MgO<17 wt %.

However, no claim is made to fibres having a SiO₂ excess as specified ofgreater than 21.8 mol %.

Further features of the invention are apparent from the appended claims.

The excess SiO₂ figure is calculated by treating all of the CaO as beingbound as CaO.MgO.2SiO₂; all of the ZrO₂ as being bound as ZrO₂.SiO₂; andthe remaining as being bound as MgO.SiO₂. The applicants also assumethat any Al₂O₃ crystallises as Al₂O₃.SiO₂. Any remaining SiO₂ is calledthe excess SiO₂.

The invention is illustrated by way of example in the followingdescription with reference to the drawings in which

FIG. 1 is a graph showing linear shrinkage with temperature for blanketscomprising the fibres A4-2 and A4-3 of Table 1 below.

FIG. 2 is a graph showing shrinkage through the height of blanketscomprising the fibres A4-2 and A4-3 of Table 1 below.

FIG. 3 is a graph showing shrinkage of preforms produced from fibresA4-1, A4-2 and A4-3 of Table 1 below.

Table 1 shows compositions extracted from WO89/12032, WO93/15028,WO94/15883, and WO97/16386 together with A4, a target composition fibrehaving the composition:—

-   -   SiO₂ 65 wt %    -   CaO 19.5 wt %    -   MgO 15.5 wt %        and A4-1, A4-2, and A4-3, which are analysed fibre samples.

The fibres extracted from the data of WO89/12032 (referred to asManville fibres), WO93/15028, WO94/15883, and WO97/16386 (referred to asUnifrax fibres) are those for which the SiO₂ excesses as specified isless than than 21.8 mol % and for which the amount of MgO in mol % isgreater than the amount of CaO in mol %.

A4-1 was produced as bulk fibre; A4-2 was produced as needled blankethaving a density of approximately 96 kg.m⁻³; and A4-3 was produced asneedled blanket having a density of approximately 128 kg.m⁻³.

In Table 1 shrinkages are indicated from the documents concerned or, forA4-1, A4-2, and A4-3, from measuring the shrinkage of vacuum formedpreforms of the fibres concerned.

TABLE 1 Shrinkage at Composition wt % Composition mol % SiO₂ Fibre 1260°C. CaO MgO ZrO₂ Al₂O₃ TiO₂ SiO₂ Others CaO MgO ZrO₂ Al₂O₃ TiO₂ SiO₂Excess 924 19.78 14.54 0.66 2.57 61.32 19.99 20.44 0.30 1.43 57.84 15.68SW-A1 20.50 15.20 1.10 63.70 20.16 20.79 0.00 0.59 58.46 16.92 B5 6.0019.90 15.10 0.10 0.20 64.20 0.40 19.71 20.80 0.05 0.11 59.34 18.68 75720.92 15.22 0.00 0.20 62.60 20.79 21.04 0.00 0.11 58.06 16.13 A4-1 1.8620.20 15.50 0.26 64.60 0.07 19.76 21.10 0.00 0.14 59.00 18.00 A4-2 3.2520.20 15.50 0.30 64.50 0.06 19.78 21.11 0.00 0.16 58.95 17.89 A4-3 2.7620.20 15.60 0.28 64.70 0.07 19.72 21.18 0.00 0.15 58.95 17.9 A4 target19.50 15.50 65.00 19.17 21.20 0.00 0.00 59.64 19.27 SW-A2 21.40 15.400.80 60.80 21.40 21.42 0.00 0.44 56.74 13.49 SW-A 20.50 15.50 3.30 59.3020.66 21.73 0.00 1.83 55.78 11.56 932 21.60 15.65 0.11 1.50 59.85 21.5821.75 0.05 0.82 55.80 11.60 Manville104 17.70 16.30 1.83 64.10 17.4922.40 0.00 0.99 0.00 59.11 18.23 B9 5.00 18.10 17.10 0.10 0.20 64.400.20 17.72 23.29 0.04 0.11 58.84 17.69 971 23.92 17.36 0.05 0.74 56.8223.56 23.79 0.02 0.40 52.23 4.47 B8 6.90 18.80 17.90 0.30 0.20 63.000.20 18.30 24.24 0.13 0.11 57.23 14.46 B16 4.30 15.10 18.10 0.30 0.100.10 66.00 0.20 14.78 24.65 0.13 0.05 0.07 60.31 20.69 A2-12 16.55 18.000.05 0.33 63.56 16.37 24.76 0.02 0.18 58.67 17.34 A2-30 16.06 18.21 0.000.40 63.68 15.89 25.07 0.00 0.22 58.82 17.64 A2-23 18.59 18.78 0.05 0.4860.20 18.37 25.82 0.02 0.26 55.53 11.06 71 24.04 19.66 0.00 0.20 54.6823.44 26.67 0.00 0.11 49.77 −0.45 A2-19 18.48 19.74 0.00 0.54 58.7118.29 27.18 0.00 0.29 54.24 8.47 A2-21 13.74 19.98 0.13 0.34 64.16 13.5127.34 0.06 0.18 58.90 17.81 Unifrax comp 13.10 0.77 16.90 34.10 0.9746.40 0.92 28.11 18.55 0.64 51.78 3.56 13 A2-24 13.62 22.74 0.08 0.3161.38 13.25 30.79 0.04 0.17 55.76 11.51 Manville105 9.74 23.10 2.1565.10 9.38 30.95 0.00 1.14 0.00 58.53 17.05 Manville79 8.67 24.00 0.0267.20 8.27 31.86 0.00 0.01 0.00 59.86 19.71 A2-25 10.99 24.18 0.07 0.3362.36 10.66 32.64 0.03 0.18 56.48 12.97 Unifrax comp 23.40 0.89 21.7024.10 0.90 51.90 0.98 33.18 12.05 0.54 53.24 6.49 14 A2-35 8.88 24.880.47 0.29 64.12 8.56 33.37 0.21 0.15 57.71 15.41 Manville78 6.43 26.5067.10 6.07 34.80 0.00 0.00 0.00 59.13 18.25 A2-34 6.63 26.20 0.80 0.2364.85 6.37 35.01 0.35 0.12 58.15 16.29 Unifrax comp 25.00 0.77 25.5016.90 0.76 55.70 0.80 36.82 7.98 0.43 53.96 7.93 15 Manville77 4.0228.70 0.59 66.10 3.79 37.68 0.00 0.31 0.00 58.22 16.44 Unifrax 42 2.000.30 29.75 0.58 0.62 68.63 0.28 38.92 0.25 0.32 60.23 20.47 Manville1062.70 29.70 1.56 65.60 2.54 38.94 0.00 0.81 0.00 57.71 15.41 Manville801.60 30.10 68.40 1.49 39.02 0.00 0.00 0.00 59.49 18.98 Manville71 3.1230.10 1.15 65.40 2.92 39.26 0.00 0.59 0.00 57.23 14.45 Manville76 3.1230.10 1.15 65.40 2.92 39.26 0.00 0.59 0.00 57.23 14.45 Unifrax 47 7.700.25 30.26 0.01 1.86 67.53 0.23 39.56 0.00 0.96 59.24 18.48 Unifrax 409.20 0.27 30.57 0.58 0.92 67.52 0.25 39.90 0.25 0.47 59.13 18.25 7653.90 35.07 0.00 2.12 57.78 3.62 45.26 0.00 1.08 50.04 0.07

It can be seen that the fibres according to the present invention showlower shrinkage at 1260° C. than do the exacted fibres other than fibreUnifrax 42 which has a radically different composition.

In FIGS. 1-3, graphs show the shrinkage characteristics of the fibresA4-1, A4-2, and A4-3 after 24 hours exposure to the indicatedtemperatures it can be seen that the fibres are readily usable attemperatures of 1200° C. or more.

Table 2 below shows the results of solubility tests on the fibres inphysiological saline solution indicating that the fibres are soluble inbody fluids. (See WO94/15883 for a discussion of methods of measuringsolubility). Pairs of results are indicated for separate tests on eachsample as is a mean total solubility.

TABLE 2 Solubility (ppm) Fibre type CaO MgO SiO₂ Total Mean Total A4-1102 115 171 388 383 105 110 162 377 A4-2 105 116 172 393 395 114 117 166397 A4-3 114 123 166 403 411 114 128 177 419

A typical range of compositions for fibres of the present inventionwould be

-   -   SiO₂ 65±0.5 wt %    -   CaO 20±0.5 wt %    -   MgO 15±0.5 wt %

Further tests were made on fibres having the inventive composition ofSiO₂ 65%, CaO 19.5%, MgO 15.5% in comparison with Superwool 607™, afibre having the nominal composition (by weight) of SiO₂ 65%, CaO 29.5%,MgO 5.5%, and Al₂O₃<1%; Superwool 612™, a fibre having the nominalcomposition (by weight) of SiO₂ 64.5%, CaO 17%, MgO 13.5%, ZrO₂ 5%; andrefractory ceramic fibre having the nominal composition SiO₂ 56%, Al₂O₃44%.

The first test was aimed at indicating the amount of dust that might bereleased on handling. The test comprised the determination of the amountof dust present in a sample of blanket made from the respective fibres.The samples of blanket were vibrated on a Fritsch Analysette type 3010vibratory sieve shaker, which was set for a frequency of 3000 Hz andvertical amplitude of 0.5 m The apparatus was equipped with a 1.6 nmsieve and a pan. In the test method a sample of blanket 135 min×135 mmwas placed on the sieve and vibrated for 10 minutes. The materialcollected in the pan was weighed and expressed as a percentage of theoriginal weight of the sample. The results were as indicated below:—

Fibre Material Percent dust released Superwool 607 ™ 0.16% Inventivematerial 0.18% Refractory ceramic fibre 0.25% Superwool 612 ™ 0.36%

From this it can be se that the inventive fibre is of comparable lowdustiness to Superwool 607™.

The second test made was to look to the shrinkage behaviour of blanketformed from the inventive fibre and the two Superwool™ fibres at hightemperatures. Samples of blanket were exposed to specified temperaturesfor 24 hour periods and their linear shrinkage measured. The results areindicated in Table 3 below.—

TABLE 3 Temperature Sample 1050° C. 1110° C. 1150° C. 1200° C. 1250° C.1300° C. Inventive fibre 0.8 0.6 1.0 1.0 1.5 4.2 Superwool 612 ™ 0.7 1.01.1 1.7 1.8 12.1 Superwool 607 ™ 0.4 0.4 0.5 0.6 4.8 7.8

This shows that the inventive fibre is comparable in performance withboth Superwool™ fibres up to 1200° C. At 1250° C. the Superwool 607™fibre shows a shrinkage of 4.8% (which would be considered as too high ashrinkage for most applications). At 1300° C. the inventive fibre whilestill showing a high shrinkage of 4.2% is the best of the three fibrestested.

A further series of tests were made to produce fibres on a productionscale and the compositions of fibres obtained were as set out in Table 4below. All showed low shrinkage at 1250° C. (shrinkages were measured bydifferent methods to Table 1 and are not directly comparable). Incombination with the results of Table 1, this shows samples of usablecharacteristics having compositions consisting essentially of (in wt%):—

CaO 18.7 to 20.2 MgO 14.47 to 15.9  SiO₂ 64.5 to 65.1 Al₂O₃   0 to 0.56

The fibres of the present invention therefore have a high solubility(desired to permit fibres to be cleared from the body quickly); a lowdustiness (desired to reduce the amount of fibre that can be inhaled),and good high temperature characterstics.

TABLE 4 Linear shrinkage (%) Composition wt % Composition wt % SiO₂Fibre at 1250° C. CaO MgO ZrO₂ Al₂O₃ TiO₂ SiO₂ Others CaO MgO ZrO₂ Al₂O₃TiO₂ SiO₂ Excess SM 0.80 20.10 15.00 0.06 65.00 19.77 20.52 0.00 0.0359.67 19.35 TCI 0.78 18.90 15.50 0.38 65.10 18.63 21.26 0.00 0.21 59.9019.81 TCUK no preform 18.70 15.90 0.44 64.80 18.41 21.78 0.00 0.24 59.5619.13 made TCUK2 2.6 19.30 14.47 0.56 0.03 64.54 0.40 19.30 20.13 0.000.31 60.24 20.50 (measured at 1300° C.)

1. A fibre having a maximum use temperature of 1200° C. or more whichcomprises:— SiO₂>64.25 wt % CaO>18 wt % MgO<17 wt % and in which theamount of MgO in mol % is greater than the amount of CaO in mol % and inwhich the SiO₂ excess as specified is no greater than 21.8 mol %.
 2. Afibre as claimed in claim 1 and comprising:— CaO<21 wt %.
 3. A fibre asclaimed in claim 2 and comprising:— CaO<20.5 wt %.
 4. A fibre as claimedin claim 1 and comprising:— CaO>19 wt %.
 5. A fibre as claimed in claim4 and comprising:— CaO>19.5 wt %.
 6. A fibre as claimed in claim 1 andcomprising:— MgO>14.25 wt %.
 7. A fibre as claimed in claim 6 andcomprising:— MgO>14.75 wt %.
 8. A fibre as claimed in claim 7 andcomprising:— MgO>15.25 wt %.
 9. A fibre as claimed in claim 1 andcomprising:— MgO<16 wt %.
 10. A fibre as claimed in claim 1 andcomprising:— SiO₂ 65+/−0.5 wt % CaO 20+/−0.5 wt % MgO 15+/−0.5 wt %. 11.A fibre as claimed in claim 1 and comprising:— SiO₂ 64.5-64.7 wt % CaO19.5-20.2 wt % MgO 15.5-15.6 wt %.
 12. A fibre as claimed in claim 1 andcomprising:— SiO₂ about 65 wt % CaO about 19.5 wt % MgO about 15.5 wt %.13. A fibre as claimed in claim 1 and consisting essentially of:— CaO18.7 to 20.2 wt % MgO 14.47 to 15.9 wt % SiO₂ 64.5 to 65.1 wt % Al₂O₃ 0to 0.56 wt %.